I've had my 2009 for about 3 months and just recently took my first passenger (wife) on a ride - actually two rides (the first about 20 miles and the 2nd about 30 miles). I'm 200#, and with the factory settings, I think the bike shifted better and rode smoother with two of us. She's 125#, so you do the math.
**Cheap Mod Alert** My wife wasn't a huge fan of the seat, but she thought she could do two-up for a couple hours at most. We went to Academy Sports before our next ride and bought one of those $6 stadium gel-cushion seats. She loved it and thought it was much more comfortable. I even bought one for me to keep in my top box and use on longer rides. It really does make a difference.
Heck, I'm even thinking of cutting it to fit the seat and glueing it down. Any thoughts on that? I actually don't mind just leaving it my top box and using it when needed (it fits perfectly in the top box with room for plenty of other stuff (12-packs)). It's about 1/2 inch wide.